This invention relates generally to chassis suspension for agricultural equipment, and more specifically to methods and apparatus for a spring-cushioned suspension system for a sprayer.
High clearance agricultural vehicles have been known for years. They are particularly useful in spraying row crops. In this instance, these are typically designed for use with maturing corn of four or five feet in height and in order to avoid damage to the crop, the vehicles have a general clearance at least equal to the height of the rows of crops, (hence the vehicles are relatively tall pieces of equipment). These vehicles generally have at least two drive wheels the width of which allows the vehicle to pass between two different crop rows. The vehicles are also equipped with a boom which extends outwardly from both sides of the vehicle to spray relatively large crop areas at a time.
In one manner of application, sprays are applied to the crops during the tilling stage when the crops are quite small and a conventional ground-type crop sprayer could traverse the field without causing damage to the small plants. However, conventional ground supported crop sprayers are usually not suitable during the latter stages of growth. For example, during the stem extension stage, the likelihood of damage to the standing crops increases if the spray is applied by a ground traversing conventional crop sprayer.
Conventional crop sprayers are even more unsuitable for applying agricultural sprays during the heading and ripening stage of the crop. However, in order to obtain a good yield, it is often necessary to apply spray, for example, a fungicide, during the these stages especially to crops such as, wheat, barley, and the like. Spraying at these latter stages of growth has been typically done by aerial spraying in order to avoid damage to the standing crop. The effectiveness of aerial spraying is dependent in large part upon the weather conditions, and even then, the application of the spray is not as effective as ground spraying if damage to the standing crop can be avoided. Further, the spray must be concentrated when applied by crop aerial dusting because of the limitations of the capacity of the aerial sprayer.
Because spray vehicles operate over rough ground and in tall mature crops, various devices are used to help cushion the vehicle, operator, and boom from the effects of these rough surfaces. Most of these devices suffer from one or more disadvantages such as limited cushioning or bulkiness leading to interference with spraying the crop. A cushioned wheel arrangement, such as the front wheel suspension shown in U.S. Pat. No. 5,066,030, is available for relatively small sprayers with a single steerable wheel. However, such a suspension is not suitable for most larger sprayers or sprayers having two or more steerable wheels. Some available self-propelled sprayers have strut suspensions such as the one disclosed in U.S. Pat. No. 5,597,172. Strut shaft type suspensions may not have the ability to provide all of the traction necessary to move freely about rough terrain. Furthermore, the strut shafts may bend under rough terrain conditions thus making the vehicle less durable.
Sprayer suspensions with strut shafts may also include steel suspension springs immersed in oil. However, these often leak, and require supports with relatively large diameters both above and below the axle which interfere with the crops. Therefore, providing adequate cushioning without adversely affecting the crops continues to be a problem. Further, commercial systems with spring suspension systems have added cab roll on sloping terrain which results from compression of the springs.
U.S. Pat. No. 5,353,988 shows another suspension system. One of the drawbacks of this system is that the swing arms pivot point is high (for ground clearance) and the wheels are low. This configuration can cause problems when the vehicle hits a bump because the wheels move out as much as they do up. Thus, every bump the vehicle hits tends to shove the wheel into the crop which can damage the crop. Moreover, as the vehicle's load gets heavier or lighter, it changes its wheel track, so that when it's fully loaded it may be running over the outside rows and when it is empty it may be running over the inside rows.
Given the above-described deficiencies of existing high clearance vehicles, the industry has a continuing interest in designing such a vehicle with an improved suspension system that minimizes crop interference and bump steer problems, a smoother ride, improved boom visibility and suspension, an improved cooling system, an improved tank design, a wheel configuration which improves traction and minimizes damage to crops, and ready access to operating parts for ease in service and repair.
The above-referenced U.S. patents disclose embodiments that were at least in-part satisfactory for the purposes for which they were intended. The disclosures of all the above-referenced prior United States patent, in their entireties are hereby expressly incorporated by reference into the present application.